PLANT PHYSIOLOGY 24 1 



carbon dioxide and water and on the other not only carbohydrates j 

 but also fats and proteins; (2) the kinetic energy of sunlight is 

 necessary to produce the synthesis ; (3) oxygen is evolved. Still, 

 taking everything into consideration, it seems probable^ as 

 supported by laboratory syntheses and by the well-supported 

 claim of the presence of formaldehyde in plants, that in plants 

 the process of photosynthesis results first in the synthesis of 

 a non-carbohydrate compound, formaldehyde, from carbon di- 

 oxide and water at the same time setting free oxygen which is 

 given off by the plants, the formaldehyde then polymerizing 

 to the formation of glucose sugar which is thus the first of the 

 essential organic constituents to be formed as the direct product 

 of photosynthesis. This view, it may be said, is more generally 

 accepted than any other. 



FUNCTION OF THE PRODUCTS OF PHOTOSYNTHESIS 



Accepting, then, this view that the carbohydrate glucose is 

 the first essential compound formed, we still have the fact that 

 the final result of photosynthesis as a whole is the formation of 

 the three energy-storing substances, carbohydrates, fats and 

 proteins. All of these compounds are formed in the leaves 

 and other green parts of plants and serve as food material for 

 the plant itself, being in a condition analogous to that of digested 

 and absorbed food in animals. Let us now take up separately 

 these three groups of compounds which, either directly or in- 

 directly, are the products of photosynthesis, and follow them in 

 the fulfillment of their function as plant food. 



Carbohydrates 



This group of compounds is more abundant in plants than 

 are fats or proteins. As an energy food for the plant itself we 

 can hardly say that the carbohydrates are more important 

 than the others, but they are used more abundantly as build- 

 ing material for the plant body. This is in accord with their 

 presence in greater amounts in most parts of the plant. 



